U0676

Code

Generic U — Network/User

Lost Communication With Fuel Level Sensor A

Brand: Generic

Type: U — Network/User

Views: UK: 41 EN: 53 RU: 59

AI status

Completed

ready

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Page language: EN

Causes

Open/short in sensor wiring or network data lines (CAN/LIN)
Corroded or loose connector at fuel level sensor or gateway
Blown fuse or missing power/ground to the sensor/module
Faulty fuel level sensor/module
Missing/incorrect CAN/LIN termination or bus short to battery/ground
Software/configuration or gateway routing error

Symptoms

Fuel gauge may read erratic, stuck, or blank
Fuel level reading unavailable via scan tool
Related warnings (low fuel) may not trigger or may be false
Instrument cluster or driver information shows dash message about fuel sensor
MIL may be illuminated if controller flags related faults

What to check

Read and record U0676 plus any other U-codes and freeze frame data with a capable scan tool
Check for other modules reporting network issues (U0100, U0121, etc.)
Visually inspect wiring and connectors at the fuel tank and any in-line junctions for corrosion, water, or damage
Verify fuses and relays that supply power to the fuel tank module
Verify good ground at the fuel tank module
Check CAN/LIN bus activity using a scan tool or scope (message IDs, frequency) while monitoring for the fuel level sensor messages

Signal parameters

CAN bus: observe message ID for fuel tank module and expected message frequency (varies by vehicle, commonly 0.2–5 Hz)
CAN bus idle voltages: CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V (differential ~0–2 V); termination ≈ 60 Ω
LIN bus idle: approx. battery voltage (when driven) or pull-up level per vehicle spec
Fuel level sensor analog/resistive values if direct: typical 0–5 V signal or variable resistance (vehicle-specific)
Power feed to sensor/module: battery voltage (approx. 12 V) with ignition on
Module ground: near 0 V with good continuity

Diagnostic algorithm

Confirm the DTC is current: connect a scan tool, record the code(s), freeze frame, and live data. Note whether the code is steady or intermittent.
Check for correlated codes: diagnose any network-wide faults first (multiple U-codes may indicate bus short or termination failure).
Visual inspection: inspect fuel tank area connectors, wiring harness, and any intermediate junctions for corrosion, water ingress, or mechanical damage.
Verify power and ground: with ignition ON, verify battery voltage at the fuel level sensor/module power pin and near 0 V at ground. Repair any open or high-resistance connections.
Verify vehicle network signals: use a scan tool or oscilloscope to check for CAN/LIN activity. Confirm whether the fuel level module message ID is present and at expected frequency. If message absent, isolate to sensor/module side.
Check bus integrity: measure CANH/CANL voltages with key on, engine off; measure termination resistance between CANH and CANL (≈60 Ω). Repair short/open as required.
Probe sensor outputs: if sensor is analog/resistive, measure sensor voltage or resistance while moving the float (if accessible) to confirm operation.
Repair or replace: repair wiring/connector faults, replace blown fuses, repair bus short, or replace fuel level sensor/module if confirmed defective.
Reprogram/Verify: if module replacement occurred, ensure any required programming/configuration is completed and clear codes.
Retest: clear DTCs and verify system returns to normal operation under the conditions that originally set the code; road test and re-scan.